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For electronic equipment, a certain amount of heat will be generated when working, so that the internal temperature of the equipment will rise rapidly. If the heat is not sent out in time, the equipment will continue to heat up, the device will fail due to overheating, and the reliability of electronic equipment will decline. Therefore, it is very important to heat the Printed Circuit Board.
1. Add heat dissipation copper foil and adopt large area power supply ground copper foil.
According to the above figure, we can see that the larger the area of the copper skin, the lower the junction temperature
According to the above figure, it can be seen that the larger the copper coating area, the lower the junction temperature.
2. Hot via
Thermal via can effectively reduce the junction temperature of the device and improve the uniformity of the temperature along the thickness direction of the single board, which makes it possible to adopt other heat dissipation methods on the back of PCB. The simulation results show that compared with the non thermal vias, the junction temperature can be reduced by about 4.8 ° C when the thermal power consumption is 2.5W, the spacing is 1mm, and the temperature difference between the top and bottom of PCB is reduced from 21 ° C to 5 ° C. Compared with 6x6, the junction temperature of the device is increased by 2.2 ° C after the thermal via array is changed to 4x4, which is worthy of attention.
3. Copper is exposed on the back of IC to reduce the thermal resistance between copper sheet and air
Several heat dissipation methods of PCB
4. PCB layout
Requirements for high power and thermal sensitive devices.
a. The thermal sensor is placed in the cold air area.
b. The temperature detector is placed in a hot position.
c. The devices on the same printed circuit board shall be arranged according to their calorific value and heat dissipation degree as far as possible. The devices with small heat output or poor heat resistance (such as small signal transistors, small scale integrated circuits, electrolytic capacitors, etc.) shall be placed in the cooling air Upstream (inlet), devices with high heat output or good heat resistance (such as power transistors, large scale integrated circuits, etc.) are placed downstream of the cooling air flow.
d. In the horizontal direction, high-power devices should be arranged as close as possible to the edge of the printed circuit board in order to shorten the heat transfer path; in the vertical direction, the high-power devices should be arranged close to the top of the printed circuit board as far as possible, so as to reduce the influence of these devices on the temperature of other devices.
e. The heat dissipation of printed circuit board in the equipment mainly depends on air flow, so the air flow path should be studied in the design, and the device or printed circuit board should be reasonably configured. When air flows, it always tends to flow at the place with small resistance, so when configuring devices on the printed circuit board, it is necessary to avoid leaving a large space in a certain area. The configuration of multiple printed circuit boards in the whole machine should also pay attention to the same problem.
f. The temperature sensitive devices are placed in the temperature area (such as the bottom of the equipment). Do not put them directly above the heating devices. Multiple devices are staggered on the horizontal plane.
g. The power consumption and heating devices are arranged near the heat dissipation position. Do not place the device with high heat in the corner and edge of PCB, unless there is heat sink near it. In the design of power resistance, the larger devices should be selected as much as possible, and there should be enough heat dissipation space when adjusting the layout of printed circuit board.
